Tuberculosis (TB) was responsible for almost one billion deaths in the 20th century. It is epidemic in the developing world and immigrants introduce TB to developed nations. TB control requires treatment for LTBI and active disease, as well as adherence to medical regimens. We propose to determine the effectiveness of a public health model of LTBI control among high-risk adolescents. The integration of behavioral science, medical services, parent instruction, assistance from schools and clinics, all coordinated by the County Health Department, is based on recommendations from CDC. The effectiveness of this system is dependent, in part, on patients' adherence. The proposed study will demonstrate a public health program for TB control among PPD+ adolescents and conduct a controlled trial of peer counseling plus parent education for adherence to INH. We will test these procedures with high-risk adolescents, from Latino, Asian, and foreign-born populations, for whom latent TB is epidemic. High school students will be screened and 300 PPD+ male and female youth (13-18 yrs.) will be assigned at random to either usual medical care plus non-directed (attention control) counseling, or to usual medical care plus peer adherence counseling and parent instructions to support adherence. Parents of eligible youth will be provided instruction about TB, their child's risk, and preventive treatment. Parents of youth assigned to the peer counseling condition will obtain additional instruction to use contingency management to support their child's adherence to INH. Clinic personnel will receive continuing medical education (CME) related to TB. The primary specific aims are: 1) to determine whether peer counseling increases adherence to prescribed INH medication relative to controls and 2) to determine the cost and cost effectiveness of the intervention. We will determine if training increases parents' and professionals' knowledge of TB control and we will explore possible determinants of adherence to INH. Reported adherence (number of pills taken/month), pill counts and electronic dispenser measures will be verified by monthly impromptu urine assays. Multivariate statistical tests will be used to determine possible mediators/moderators and other predictors of adherence over 12 months. The assessment of both outcomes and relative costs will inform the effectiveness and practicality of a larger scale TB prevention program for high-risk youth in San Diego and other regions where TB is epidemic.